Field of the Invention
The present invention relates to a technology for acquiring information regarding a distance of a subject in an imaging apparatus.
Description of the Related Art
Imaging apparatuses perform processes of generating distance maps indicating distributions of distances to subjects (hereinafter referred to as subject distances) based on captured images in order to acquire depth information regarding images. In these processes, it is necessary to improve detection precision of the subject distances. As factors deteriorating the detection precision, there are aberration of curvature of field or the like caused due to a manufacturing error or optical characteristics of design of an imaging lens, an influence of imaging surface flatness of an image sensor, and the like. When an imaging surface is not an ideal plane with no inclination, an error occurs in a subject distance. Hereinafter, an ideal flat imaging surface with no inclination is referred to as an “ideal imaging surface” and correction for approaching the ideal imaging surface is referred to as an “imaging surface correction.”
Japanese Patent Laid-Open No. 2014-126858 discloses a technology for calculating a distribution of a subject distance in a photographing scene based on a focus evaluation value obtained through AF (automatic focus adjustment) scan. According to the position of a focus detection region, correction amounts of aberration of curvature of field or the like caused due to a manufacturing error or optical characteristics of design of an imaging lens and imaging surface flatness of an image sensor are calculated. By detecting a focus lens position at which a focus evaluation value is peak for each focus detection region and correcting the focus lens position according to the position of the focus detection region, it is possible to improve precision of the distribution of the subject distance.
In Japanese Patent Laid-Open No. 2014-126858, a process of calculating and correcting a defocus correction amount of an imaging surface is performed by approximating imaging surface characteristics due to a manufacturing error or optical characteristics of design of an imaging lens, and imaging surface flatness of an image sensor by a quadratic function. The quadratic function for the calculation of the correction amounts has no coefficients corresponding to imaging surface characteristics due to a manufacturing error or optical characteristics of design of an imaging lens and imaging surface flatness of an image sensor. That is, because of an added coefficient, the technology is assumed to be applied to a lens integrated type imaging apparatus. In contrast, in a lens interchangeable type imaging apparatus in which a lens device is mounted on a camera body for use, when a combination of an imaging lens and the camera body is changed, a correction amount of an imaging surface has to be calculated according to the combination. For this reason, it is necessary to separately have imaging surface correction information of an imaging lens and imaging surface correction information of an image sensor.